Summary

The pancreas is an organ containing two distinct populations of cells, the exocrine cells that secrete enzymes into the digestive tract, and the endocrine cells that secrete hormones into the bloodstream. It arises from the endoderm as a dorsal and a ventral bud which fuse together to form the single organ. Mammals, birds, reptiles and amphibians have a pancreas with similar histology and mode of development, while in some fish, the islet cells are segregated as Brockmann bodies. Invertebrates do not have a pancreas, but comparable endocrine cells may be found in the gut or the brain. The early pancreatic bud shows uniform expression of the homeobox gene IPF-1 (also known as IDX-1, STF-1 or PDX), which when mutated to inactivity leads to total absence of the organ. The occurrence of heterotopic pancreas in the embryo, and also the metaplasias that can be displayed by a regenerating pancreas in the adult, both suggest that only a few gene products distinguish the pancreatic cell state from that of the surrounding tissues of duodenum, gall bladder and liver. In the developing pancreatic buds, the endocrine cells start to differentiate before the exocrine cells, and co-expression of different hormones by the same cell is often observed at early stages. Although pancreatic endocrine cells produce many gene products also characteristic of neurons, evidence from in vitro cultures and from quailchick grafts shows that they are of endogenous and not of neural crest origin. Observational studies suggest strongly that both endocrine and exocrine cells arise from the same endodermal rudiment. Development of the pancreas in embryonic life requires a trophic stimulus from the associated mesenchyme. In postnatal life, all cell types in the pancreas continue to grow. Destruction of acinar tissue by duct ligation or ethionine treatment is followed by rapid regeneration. Surgical removal of parts of the pancreas is followed by moderate but incomplete regeneration of both acini and islets. Poisoning with alloxan or streptozotocin can lead to permanent depletion of beta cells. Although the cell kinetics of the pancreas are not understood, it seems likely that there is a continuous slow turnover of cells, fed from a stem cells population in the ducts, and that the controls on the production rate of each cell type are local rather than systemic.

In a new poster and article, Sinem Karaman, Veli-Matti Leppänen and Kari Alitalo provide an overview of the VEGF signalling pathway and highlight the functions of VEGF/VEGFR signalling in blood and lymphatic vessel development and pathology.

In regenerating tissues, polyploidization is a commonly used strategy to compensate for cell loss. Jan Inge Øvrebø and Bruce A. Edgarreview how such tissues are less dependent on resident stem cells, an advantage that may be exploited in regenerative therapy.

Parasitic plants rely on the haustorium, a specialised root structure that invades host root vasculature to derive nutrients and water. A recent Research Article addresses the developmental origins of these crucial structures in the facultative root parasite Phtheirospermum japonicum. The Node caught up with first author Takanori Wakatake and his supervisor Ken Shirasu to find out more about the story.

The Node has digitised a network originally made at the BSDB Spring Meeting in Warwick that shows the connections between attendees and their advisers. You can add yourself if you’re not on there yet, and explore the digitised network.

Development is pleased to welcome submissions for an upcoming special issue on ‘Development at the single cell level’, guest-edited by Allon Klein and Barbara Treutlein. This special issue aims to showcase the best research in stem cell and developmental biology, building on the rapidly evolving tools of single cell analysis. Submission deadline: 31 October 2018.

Shikha Nayar highlights a preprint from Catherina G. Becker and co-workers that sheds light on key immune mechanisms and spatiotemporal dynamics that orchestrate spinal cord regeneration in zebrafish. This preLight includes a response from the author team on the surprising complexity of regeneration in their study.

We are pleased to announce that Development will now feature recent preLights that are of interest to the developmental biology community as part of each issue's Table of Contents.